"This is huge news for Santorum," says Charlie Arlinghaus, who directs a conservative think tank in New Hampshire. "I don't think there's a way to spin the results without saying he's the big winner tonight."

Santorum's surge came at just the right time. He went from single digits in the polls in Iowa to a virtual tie in just one week with Romney, the former Massachusetts governor. (Romney finished with 30,015 votes to Santorum's 30,007 votes, the Iowa Republican Party announced Wednesday morning.)

And Santorum, the former Pennsylvania senator, now stands as the most viable conservative alternative to Romney.

But Romney is favored to win the next contest, the New Hampshire primary, which will be held next Tuesday. And Santorum has yet to break out of the single digits in other early-voting states or in national tracking polls.

"Santorum will have a hard time with this kind of result raising the kind of money and organization he needs almost immediately," says Art Sanders, a political scientist at Drake University in Des Moines, Iowa.

Latest In A Long Line

Republicans have shifted their support from one "anti-Romney" to the next over the past several months, favoring a series of candidates with polling leads that evaporated almost as soon as they were run up.

That same sort of hunger for an alternative to Romney has not been as apparent in New Hampshire, where Romney is well-known from his stint as the governor of a neighboring state.

"There's no question that nobody's going to beat Romney here," says Arlinghaus, head of the Josiah Bartlett Center for Public Policy in New Hampshire. "Romney is going to win New Hampshire and win by a substantial margin."

A clear win in Iowa, coupled with a victory in New Hampshire, would have given Romney a powerful one-two punch to land against his rivals. But the jump ball in Iowa keeps open the question of when — or whether — Romney can firm up his lead.

A Ceiling For Santorum?

Romney would be in a worse position now if he'd finished in an Iowa caucus tie with either Texas Gov. Rick Perry or former House Speaker Newt Gingrich, says Jack Pitney, a political scientist at Claremont McKenna College in California, because of their superior name recognition and fundraising ability.

Still, Pitney says, a virtual tie with "somebody who used to be an asterisk is nothing to write home about."

Santorum's timing was perfect. After laying the groundwork in Iowa for months, visiting every corner of the state, he was able to take advantage of some key endorsements and also momentum that pushed him forward so late that his opponents' attacks came too late to resonate.

Santorum will press his case in a pair of debates scheduled for this weekend. But he hasn't been able to devote anything like the same amount of time to New Hampshire that he has spent in Iowa.

A Potential Game-Changer

Romney and Ron Paul, the Texas congressman who finished a close third in Iowa, both have much stronger organizations in New Hampshire than Santorum.

So does Jon Huntsman, the former Utah governor who decided to skip Iowa to devote his attention full time to New Hampshire.

"I don't think anyone here suddenly expects Rick Santorum to give Romney a run for his money in this state," says Dean Spiliotes, founder of the blog NHPoliticalCapital.com.

Even after his success in Iowa, it's not inconceivable that Santorum could still finish fourth in New Hampshire, Spiliotes says. On the other hand, his bounce out of Iowa might just move him ahead of most, if not all, of the pack.

Romney would face a real fight if Santorum manages to finish even a distant second next week, Spiliotes says.

"If he comes in a reasonable second place to Romney, that shows some viability beyond this one contest," he says. "That could be a game-changer."

Built To Last

Romney supporters say they never expected to end the nomination process with a single contest. They say he has the infrastructure and strategy in place to last over the long haul.

"We always said this campaign is a national effort," says David Oman, a Romney supporter in Iowa and former gubernatorial candidate there. "The Romney campaign has been assembled to go all the way. Santorum has to go a huge distance to catch Romney."

But even some Romney supporters acknowledge that Santorum has come a very long way just in the past few days.

"I think we'll see an elevated level of activity, particularly for Santorum, who had some organizational strength here before he basically went to live in Iowa," says Tom Rath, a former New Hampshire state attorney general and Romney backer.

"This will make for a very interesting and competitive week here in New Hampshire," Rath says.